A containment system and method for using said containment system

ABSTRACT

A containment system for recovering hydrocarbon fluid from a leaking device comprising a dome sealed to the seafloor around the leaking device and forming a cavity for accumulating hydrocarbon fluid. The system comprises a lower closing assembly for closing a lower opening during descent of the system to the seafloor.

RELATED APPLICATIONS

The present application is a National Phase entry of PCT Application No.PCT/IB2014/002203, filed Jun. 16, 2014, said application being herebyincorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention concerns a containment system for recoveringspilled oil that is leaking under water.

BACKGROUND OF THE INVENTION

The present invention concerns more precisely a containment system forrecovering a hydrocarbon fluid from a leaking device that is situated atthe seafloor and that is leaking the hydrocarbon fluid from a well.

Recovering oil that is leaking from an under water oil device is a greatproblem, especially for oil device that are installed at deep sea floor.

The explosion on the “Deepwater Horizon” platform in the Gulf of Mexicodemonstrated how much such a containment system is difficult to control.

One of the main problems was the formation of hydrates that clogged theused containment system.

For example, at a depth of around 1500 meters or more, the sea water iscold (for example around only 5° C.) and at a high pressure. Theseenvironment conditions may transform the sea water and hydrocarbon fluidinto hydrates having a quasi-solid phase and which can fill and cloggedany cavity.

Hydrates inhibitors like methanol could be injected to avoid hydrateformation. But, the needed quantity of such chemical is very large andinhibitors are also pollution for the environment.

Heating of the containment system could be used to avoid hydrateformation. But, as the volume of cavity of the containment system isgreat, the heating is slow and amount of heat is too important.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a containment systemthat avoids the formation of hydrates inside the dome.

To this effect, the containment system of present invention is adaptedto be landed at the seafloor corresponding to a base level of thecontainment system. It comprises:

-   -   a dome intended to be secured to the seafloor around the leaking        device and forming a cavity under said dome, said cavity being        adapted to completely surround and include the leaking device,        and to accumulate hydrocarbon fluid coming upwardly from the        leaking device, said dome comprising an upper opening to extract        the hydrocarbon fluid for recovering and a lower opening to        enter the leaking device inside the cavity,    -   an upper valve for opening or closing the upper opening, and    -   a lower closing assembly for closing the lower opening at least        during a moving of the containment system from a first location        near the sea surface to a second location near the seafloor, and        for opening the lower opening when the containment system is        being installed around the leaking device.

Thanks to these features, the volume of the cavity can be completelyisolated to the sea water during the descent of the containment systemfrom the sea surface to the seafloor.

The cavity can be easily previously filled with an anti hydrates fluidat the sea surface.

The quantity of anti hydrates fluid is enough for preventing hydratesformation inside the cavity when the containment system is installedaround the leaking device at the sea floor.

The containment system does not need additional pipes to be connectedbetween a sea surface vessel and the containment system installed at theseafloor for injecting an anti hydrates fluid during operation.

The containment system does not need additional devices to be connectedbetween a sea surface vessel and the containment system installed at theseafloor for feeding energy to the containment system. For example, itdoes not need electrical cable for supplying electrical energy to anelectric heater for heating the dome.

The anti hydrates fluid can be enclosed inside the dome and may beheated, before the containment system is made to go down to the leakingdevice.

The containment system can be installed quickly.

The containment system is cheaper.

In various embodiments of the containment system, one and/or other ofthe following features may optionally be incorporated.

According to an aspect of the containment system, the lower opening isbetween 6 and 12 meters wide, and preferably between 8 and 10 meterswide.

According to an aspect of the containment system, the dome is thermallyinsulated with an insulating material for having an overall heattransfer coefficient of the dome lower than 1 W·m⁻²·K⁻¹.

According to an aspect of the containment system, the dome comprises astructure that is rigid for building a shape of the dome.

According to an aspect of the containment system, the structure iscomposed of interconnected beams.

According to an aspect of the containment system, the dome comprises anenvelope disposed substantially inside the structure and being flexibleto adapt itself to the shape of the structure and to seal the cavity.

According to an aspect of the containment system, the envelope extendsdownwards below a lower end of the structure to form a flexible loweropening.

According to an aspect of the containment system, the dome comprises anenvelope that extends downward below a lower end of the structure toform a flexible lower opening.

According to an aspect of the containment system, the lower closingassembly comprises a narrowing mechanism that is able to close up alower end of the envelope to close the lower opening.

According to an aspect of the containment system, the lower closingassembly is a door mechanism articulated to a lower end of the dome andcomprising a driving mechanism to close or open the lower opening.

According to an aspect of the containment system, the lower closingassembly is a diaphragm mechanism positioned at a lower end of the domeand comprising a driving mechanism to close or open the lower opening.

According to an aspect of the containment system, the lower closingassembly is a door mechanism attached to a lower end of the dome andcomprising a driving mechanism to free the door and to open the loweropening.

According to an aspect of the containment system, the lower closingassembly comprises a flexible membrane, said flexible membrane beingadapted for being penetrated by the leaking device when the containmentsystem is moved so as the leaking device enters the cavity.

Another object of the invention is to provide a method for using thecontainment system for recovering hydrocarbon fluid from a leakingdevice that is situated at the seafloor and that is leaking hydrocarbonfluid from a well, said containment system being adapted to be landed atthe seafloor corresponding to a base level of the containment system.The containment system comprises at least:

-   -   a dome intended to be secured to the seafloor around the leaking        device and forming a cavity under said dome, said cavity being        adapted to completely surround and include the leaking device,        and to accumulate hydrocarbon fluid coming upwardly from the        leaking device, said dome comprising an upper opening to extract        the hydrocarbon fluid for recovering and a lower opening to        enter the leaking device inside the cavity,    -   an upper valve for opening or closing the upper opening, and    -   a lower closing assembly for closing and opening the lower        opening.

The method of the invention comprises the following successive steps:

a) providing a containment system at a first location near sea surface,

b) closing the upper valve and the lower closing assembly, and fillingthe cavity with an anti hydrates fluid,

c) making the containment system going from the first location down to asecond location near the leaking device,

d) connecting a pipe to the upper opening,

e) opening the lower opening by the lower closing assembly,

f) moving the containment system so as the leaking device enters thecavity,

g) opening the upper valve for recovering the hydrocarbon fluid.

Thanks to the above method, the dome can be installed above the leakingdevice very quickly with a very large quantity of anti hydrates fluid.Hydrates formation inside the cavity is then prevented.

In preferred embodiments of the method proposed by the invention, oneand/or the other of the following features may optionally beincorporated.

According to an aspect of the method, the anti hydrates fluid is heatedbefore the filling step b).

According to an aspect of the method, the anti hydrates fluid comprisesone or a combination of the fluid components chosen in the list ofwater, salted water, dead oil, an alcohol, an ethanol, a methanol, aglycol, an ethylene glycol, a diethylene glycol, and a low-dosagehydrate inhibitor (LDHI).

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention will be apparent from thefollowing detailed description of at least one of its embodiments givenby way of non-limiting example, with reference to the accompanyingdrawings. In the drawings:

FIG. 1 is a schematic view of a vertical cut of a containment systemaccording to a first embodiment of the invention, said figure showingthree views of the same containment system during installation;

FIG. 2 is a schematic view of a vertical cut of a containment systemaccording to a second embodiment of the invention;

FIG. 3 is a schematic view of a vertical cut of a containment systemaccording to a third embodiment of the invention;

FIGS. 4 to 9 are an exemplary of a containment system according to thefirst embodiment of FIG. 1;

FIG. 10 is an exemplary of a containment system according to secondembodiment of FIG. 2; and

FIG. 11 is a zoomed view of a fastening means between two modules of acontainment system as on FIGS. 4-10.

In the various figures, the same reference numbers indicate identical orsimilar elements. The direction Z is a vertical direction. A direction Xor Y is a horizontal or lateral direction. These are indications for theunderstanding of the invention.

MORE DETAILED DESCRIPTION

FIG. 1 is a first embodiment of a containment system 1 according to theinvention. This figure comprises three views of the same containmentsystem 1 during installation steps: left view is the preparation step ata first location near the sea surface 4, the central view is the openingstep at a second location near the seafloor 5, and the right view is thelanding step around the leaking device 2.

This containment system 1 is adapted for recovering hydrocarbon fluidfrom a leaking device 2 that is situated at a seafloor 5 of a deepoffshore installation. The leaking device 2 is for example the wellitself, a pipeline, a blow out preventer device, a wellhead or anydevice connected to the wellhead. The leaking device 2 is thereforeusually a large device. It may be larger than 5 m. The seafloor 5 is forexample at more than 1500 meters deep below the sea surface 4, and nowit can be at a very deep depth at more than 2500 meters deep below thesea surface 4. At this depth, the sea water is cold, for example aroundonly 5° C. and at high pressure.

The hydrocarbon fluid may be liquid oil, natural gas, or a mix of them.

The leaking device 2 is leaking a hydrocarbon fluid from an underseawell 3. The hydrocarbon fluid exiting from the undersea may be ratherhot, for example above 50° C. However, the environment cold temperatureand high pressure may transform the sea water and hydrocarbon fluid intohydrates having a quasi-solid or solid phase. These hydrates can filland clogged any cavity.

The containment system 1 of present invention is landed and fixed to theseafloor by any means, such as anchoring or heavy weights 29 forcompensating the upward Archimedes force applied on the containmentsystem 1 by the hydrocarbon fluid that is lighter than the sea water(lower mass density), or such as piling with one or more piles forfixing the containment system to the seafloor. The seafloor correspondsin the present description to a base level of the containment system 1.The other levels are defined going upwards, in the vertical direction Ztowards the sea surface 4.

The containment system 1 of present invention comprises a dome 20intended to be secured to the seafloor around the leaking device 2 andforming a cavity 21 under said dome 20, said cavity being adapted tocompletely surround and include the leaking device, and to accumulatethe hydrocarbon fluid coming upwardly from the leaking device.

The dome 20 comprises:

-   -   at least one upper opening 22 located above said dome so as to        extract the hydrocarbon fluid for recovering, and    -   a lower opening 26 so as to enter the leaking device 2 into the        cavity 21 of the dome.

The upper opening 22 is a small opening for connecting a pipe, whereasthe lower opening is a wide opening for receiving the leaking device.

The dome 20 is preferably fixed and/or sealed to the seafloor.

For example, the dome 20 comprises foot 20 c having heavy weights forsealing and securing the dome 20 to the seafloor.

The term “dome” means here a general enclosure or container having adownwardly opened portion so as to be positioned above and to enclose amember. The dome has preferably a lateral portion (like a verticalcylinder) that extends substantially vertically from a base level to anupper level and an upper portion (like a cap) that extends horizontallyfrom the upper end of the lateral portion so as to close the upperportion. The dome has an inner cavity with a volume adapted to receivethe member. The lateral portion and/or upper portion may have some holesadapted for specific purposes (fluid exchange between the inner volumeand the outside of the dome).

The dome 20 completely surrounds the leaking device 2. In a horizontalplane (XY), the dome 20 has a closed loop shape encompassing the leakingdevice 2. Said shape may be for example a circle shape, a square shapeor any polygonal shape.

The dome 20 has a diameter D20. This outer diameter corresponds to amaximum distance between two internal points of the dome, taken in ahorizontal plane at a level near the base level BL. The diameter D20 isfor example of 6 meters or more.

The dome 20 is higher than a total height of the leaking device 2. Ithas a height H20 of approximately 3 meters or more. It completelyincludes the leaking device 2 (i.e. the part above the base level. Allthat is under the seafloor is not taken into account as the dome issealed to the seafloor).

The dome 20 defines an inner dome volume, called the cavity 21. Thisvolume is isolated (not in communication) with the environment seawater. The thermal exchange between the cold sea water and thehydrocarbon fluid is reduced. This first effect reduces the hydrateformation.

The dome 20 is a hollow structure.

The dome 20 according to the invention also comprises:

-   -   an upper valve 62 for opening and/or closing the upper opening        22, and    -   a lower closing device or assembly 40 for opening and/or closing        the lower opening 26.

Advantageously, the lower closing assembly 40 is controlled so as:

-   -   to close the lower opening 22 during a descent (a moving) of the        containment system 1 from a first location near the sea surface        4 to a second location near the sea floor 5, and    -   to open the lower opening 22 when the containment system 1 is        ready for installation around the leaking device, i.e. just        before the installation.

For example (first example):

-   -   the leaking device 2 may extend 6 meters in all directions;    -   the dome may be 7 meters in all directions, having a volume of        approximately 350 m³.

For example (second example), the leaking device is bigger (e.g. when itis a Christmas tree having a blowout preventer):

-   -   the leaking device 2 may extend 9 meters in all directions;    -   the dome 20 may be 10 meters in all directions, corresponding to        a very large volume of 1000 m³.

The dome 20 is landed on the seafloor and contains the leaking device 2.It is a hollow structure having:

-   -   an upper portion 24 extending in a radial direction to an outer        peripheral end 24 a, said radial direction being perpendicular        to the vertical direction AX (equal to direction Z on the        figure), and    -   a lateral portion 25 extending from the upper portion 24        downwardly between an upper end 25 a and a lower end 25 b, said        lower end 25 b comprising for example the foot 20 c.

The lateral portion 25 has said diameter D20. Its inner diameter iswider than a total wide of the leaking device 2. For example, the innerdiameter is of 6 meters or more.

The lateral portion 25 of the dome is downwardly opened so as tosurround the leaking device 2.

The dome 20 comprises downwardly a lower opening 26 so as the dome canbe landed around the leaking device 2. The lower opening 26 has a sizeadapted to the size of the leaking device 2 (it must be larger than theleaking device). The dome 20 is then usually between 6 and 12 meterswide. Eventually, the lower opening 26 is between 8 to 10 meters wide.The size of the lower opening 26 is usually adapted (equal) to thediameter D20 of the dome 20.

The upper portion of the dome 20 comprises the upper opening 22 and isadapted to be connected to a pipe 50 for extracting the hydrocarbonfluid from the containment system 1 to a recovery boat 6 at the seasurface 4, so as the hydrocarbon fluid is recovered.

In a vertical plane (XZ), the upper portion 24 of the dome 20 may have aconvergent shape from the lateral portion 25 up to the upper opening 22.The dome 20 is a cover that can have advantageously an inverted funnelshape.

The hollow structure of the dome 20 forms a largely opened cavity 21 inthe direction to the seafloor. It is positioned above and around theleaking device 2 so as to accumulate the light hydrocarbon fluid.

The cavity 21 accumulates hydrocarbon fluid coming upwardly from theleaking device 2, i.e. oil and/or natural gas. The hydrocarbon fluidfills the upper volume of the cavity, down to an interface level IL.

The dome 20 according to the first embodiment comprises:

-   -   a structure 20 a that is rigid and that gives the general shape        to the dome, and    -   an envelope 20 b disposed substantially inside the structure 20        a, said envelope 20 b being flexible to adapt to itself to the        shape of the structure and defining an inner sealed volume, i.e.        the cavity 21 of the dome 20.

The structure 20 a is for example composed of rigid interconnectedbeams. These beams may be may of steel, or any rigid material.

The envelope 20 b is sealed to the upper portion 24 of the structure 20a along its periphery end 24 a. The envelope 20 b is a tube inside thestructure 20 a that can be compressed by control means 42 or that can befreed to be applied on the inner face of the structure 20 a.

The upper portion 24 advantageously comprises the additional outputsand/or valves needed for the operations of the containment system 1.

The envelope 20 b advantageously extends downwardly from the upperportion 24, inside the structure 20 a and below a lower end 25 b of saidstructure 20 a.

A lower end of the envelope 20 a is either closed by the lower closingassembly 40 (as seen on left view of FIG. 1) so as the lower opening 26of the dome is in the closed state, or opened (as seen on central viewof FIG. 1) so as the lower opening 26 of the dome is in the openedstate.

The lower closing assembly 40 is for example a narrowing mechanism thatcloses up a lower end of the envelope 20 b to close it (to close thelower opening 26).

This narrowing mechanism may comprise any driving mechanism to switchthe narrowing mechanism from a narrow state wherein the envelope 20 b isclosed up and an enlarged state wherein the envelope 20 b is opened.

Eventually the lower closing assembly 40 is completely disconnected fromthe envelope and falls down to the seafloor as soon as it is switched tothe enlarged state.

The driving mechanism may be controlled by an wire or wireless link, orby a remote operated vehicle (ROV).

An example of the first embodiment is also illustrated on FIGS. 4 to 9showing that the containment system 1 can be composed of a plurality ofmodules, each one being installed above the other.

The modules are for example automatically secured one to the other byfastening means 27 that automatically lock themselves when a secondmodule 20 ₂ is set down above a first module 20 ₁. The fastening meansmay be a locking collet, a twist lock system or any known self fasteningdevice.

On these figures, the dome 20 comprises three modules:

-   -   a first module 20 ₁ (FIG. 4) that is a base module, comprising        the foot portion 20 c of the dome intended for seating on the        seafloor;    -   a second module 20 ₂ (FIG. 5) that is a body module, having a        general vertical cylinder shape for forming the lateral portion        25 of the dome and the shape of the cavity 21; and    -   a third module 20 ₃ (FIG. 6) that is an upper module, forming        the upper portion 24 of the dome and comprising the envelope 20        b sealed to said upper portion.

FIGS. 7 to 9 are showing this example of containment system 1 having thethree modules assembled together. FIG. 7 is the configuration beforefiling the envelope 20 b with an anti hydrates fluid AHF. FIG. 8 is theconfiguration the envelope 20 b being filed with the anti hydrates fluidAHF and the lower closing assembly 40 being closed to keep said fluidinside the envelope and being isolated from environment (sea water).FIG. 9 is the configuration the envelope 20 b being opened so as to freethe lower opening 26 of the dome so as to be able to move thecontainment system 1 to the leaking device 2 to cover it as seen onright view of FIG. 1.

FIG. 11 shows an example of a fastening means 27 for locking a secondmodule to a first module. This fastening means is a locking collet, saidlocking collet comprising a hook rotatively articulated on a firstmodule and being biased by a spring for locking said hook to a lateralprotrusion of the second module.

Moreover, the dome 20 may comprises thermal insulating material, so asto thermally insulate the cavity 21 from the cold environment of seawater. Ideally, the dome 20 may be manufactured with at least athermally insulating material, said thermally insulating materialpreferably having a thermal conductivity lower than 0.1 W·m⁻¹·K⁻¹. Thedome 20 may have an overall heat transfer coefficient lower than 2W·m⁻²·K⁻¹, and more preferably lower than 1 W·m⁻²·K⁻¹ based on theoverall internal dome wall surface.

The following thermal insulating materials may be used: syntheticmaterial such as Polyurethane (PU) or polystyrene material, or a fibretextile with Polyvinyl chloride (PVC) coating or PU coating, or Alcryn®.The thermal insulating material may be foam, or a gel contained inside adouble wall structure.

The thermal insulating material may be inside the structure 20 a and/orthe envelope 20 b. Advantageously, the envelope 20 b is the insulatingmaterial of the dome 20.

The cavity 21 of the dome 20 (volume inside the envelope 20 b in case ofpresent first embodiment) is initially filed by an anti hydrates fluidAHF.

The anti hydrates fluid AHF may be sea water pumped near the sea surface4 via a pump. The pumped sea water may be used as it, i.e. at thetemperature of sea water at the sea surface 4, or heated by additionalmeans.

The anti hydrates fluid AHF may be water, salted water, sea water, oil,gas oil, dead oil, or crude oil.

The anti hydrates fluid AHF may be an alcohol, an ethanol, a methanol, aglycol, an ethylene glycol, a diethylene glycol, or a low-dosage hydrateinhibitor (LDHI).

The anti hydrates fluid AHF may be additionally heated by a fluid heateror not, for preventing to form hydrates. In case of use water, the antihydrates fluid AHF is preferably heated. The fluid heater may by on avessel at sea surface.

The term “heated” means having a temperature increase enough to obtainthe anti hydrates effect (no formation or no adhesion). For example, thetemperature may be increased of at least 10° C., and preferably between10° C. and 15° C. above a hydrate formation temperature. The hydrateformation temperature is determined by hydrocarbon fluid and thepressure near the leaking device 2 (i.e. the depth).Temperature-pressure curves for every hydrocarbon fluid are known, thesecurves identifying the phase changes, and more particularly conditionsfor hydrates formation.

The containment system 1 additionally comprises an output valve 62connected to the upper output opening 22 and/or pipe 50 for outputtingthe recovered hydrocarbon fluid to the recovery boat 6. The output valve62 is located in a vessel or just above the dome 20 or integrated in thedome at the upper output opening 22 (as illustrated on FIG. 1).

The containment system 1 may also comprise a exhaust output valve 64 forexample situated above the dome 20 near the upper output opening 22. Theexhaust output valve 64 is adapted for opening and/or closing the cavityto the sea environment.

The sea output valve 64 is advantageously operated opposite to theoutput valve 62: the output valve 62 is closed when the exhaust outputvalve is opened, and the output valve 62 is opened when the exhaustoutput valve is closed.

The containment system 1 may comprise other output openings and/or pipesfor feeding additionally fluids, or for extracting other fluids, liquidor gases from the cavity.

For example, the containment system 1 may comprise a drain valve forpurging or limiting the quantity of water inside the cavity 21. Saiddrain valve might be positioned proximal to the base level BL(seafloor).

Advantageously, the cavity 21 can be used as a phase separator forseparating the water and the hydrocarbon fluid, and for separating eachphase of the hydrocarbon fluid (oil, gas) so as to extract themseparately.

The cavity 21 is a volume storing a quantity of hydrocarbon fluid andabsorbing the fluctuations of hydrocarbon fluid flows.

The dome 20 comprises an over pressure valve 23 that extract fluid outof the cavity and into the environment if a pressure difference betweenthe cavity 21 and the environment exceeds a predetermined pressurelimit.

The predetermined pressure limit is for example of 10 bars, 20 bars, or50 bars. This limit has to be determined accordingly with the cavitysize and the leaking device flow.

The over pressure valve is for example a ball check valve. The ballcheck valve comprises a support element, a ball, and a spring that loadsthe ball to the support element so as to close an opening. The tuning ofthe spring load is adapted to the predetermined pressure limit.

When installed around the leaking device (right view of FIG. 1), thecavity 21 is closed, and if hydrates formation is prevented, the fluidinside the cavity is rapidly heated by the hydrocarbon fluid itselfoutputting from the leaking device 2.

The over pressure valve 23 insures that the pressure inside the cavityis not increasing, and then insuring that the containment system is notdestroyed.

The predetermined pressure limit may insure that hydrates formation isprevented.

FIG. 2 is a second embodiment of a containment system 1 according to theinvention. This containment system 1 is similar to the first embodimentas it comprises a cavity 21 that can be completely closed and thereforeisolated (and thermally insulated from environment sea water). Itcomprises the same elements as the first embodiment, and can have thesame variants as disclosed above.

The second embodiment of the containment system 1 differs in that thedome 20 does not comprise an inner envelope that extends below thestructure. The structure of the dome is sealing itself the cavity 21.This containment system 1 comprises a lower closing assembly 40 that isa lower lid or a door mechanism. It also comprises a driving mechanism41 to disconnect or free the lower closing assembly 40 from the dome 20.The driving mechanism 41 is of any type. As soon as the drivingmechanism 41 is activated (arrow F1), the lower closing assembly 40 isseparated from the dome 20 and falls for example by gravity effect asshown by the arrow F2.

FIG. 10 is presenting a more detailed example of a containment systemaccording to the second embodiment.

This example comprises a dome 20 build with three modules 20 ₁, 20 ₂,and 20 ₃.

FIG. 3 is a third embodiment of a containment system 1 according to theinvention. This containment system 1 is similar to the second embodimentas it comprises a cavity 21 that can be completely closed and thereforeisolated (and thermally insulated from environment sea water). Itcomprises the same elements as the first and second embodiment, and canhave the same variants as disclosed above.

The third embodiment of the containment system 1 differs in that thelower closing assembly 40 is composed of a door mechanism, comprisingone or more doors articulated at a lower end of the dome 20. Itcomprises a driving mechanism 41 that can be activated (arrow F1) tomove the door(s) from closed position to opened position as shown by thearrow F2. The doors opens towards the outside of the containment systemas represented on the figure, i.e. the plurality of doors opens asflower petals.

According to a forth embodiment of a containment system 1 of theinvention (not shown), similar to the second embodiment as it comprisesa cavity 21 that can be completely closed and therefore isolated, thelower closing assembly 40 is composed of a diaphragm mechanism to openand/or close the lower opening 26.

According to a fifth embodiment of a containment system 1 of theinvention (not shown), similar to the second embodiment as it comprisesa cavity 21 that can be completely closed and therefore isolated. Thisembodiment differs in that the lower closing assembly 40 is composed ofa flexible membrane closing the lower opening. The flexible membrane canbe penetrated by the leaking device itself when the containment system 1is moved so as the leaking device 2 enters the cavity. The membrane isrip apart. However, as the membrane is flexible and expandable, thecavity can be kept substantially sealed.

The method for using or installing the containment system 1 according tothe invention is now explained in regards of FIG. 1 (left to rightviews).

Therefore, the containment system 1 according to the inventioncomprises:

-   -   a dome 20 intended to be secured to the seafloor around the        leaking device and forming a cavity 21 under said dome, said        cavity being adapted to completely surround and include the        leaking device, and to accumulate hydrocarbon fluid coming        upwardly from the leaking device, said dome comprising an upper        opening 22 to extract the hydrocarbon fluid for recovering and a        lower opening 26 to enter the leaking device inside the cavity,    -   an upper valve 62 for opening or closing the upper opening, and    -   a lower closing assembly 40 for closing the lower opening before        the containment system is installed around the leaking device,        and for opening the lower opening when the containment system is        installed around the leaking device.

The method according to the invention for using or installing thecontainment system 1 comprises the following successive preparationsteps, illustrated on left view:

a) providing a containment system 1 at sea surface,

b) closing the upper valve 62 and the lower closing assembly 40, andfilling the cavity 21 with an anti hydrates fluid.

During step b), the sub-steps may be operated in any order. Preferably,the upper valve 62 and lower closing assembly 40 are closed beforefilling the cavity 21 with anti hydrates fluid. The heat of this fluidis more protected and preserved from environment.

The method further comprises the following successive opening steps,illustrated on central view:

c) making the containment system 1 going down to the sea floor near theleaking device,

d) connecting a pipe 50 to the upper opening,

e) opening the lower closing assembly 40.

The method further comprises the following successive landing steps,illustrated on right view:

f) moving the containment system so as the leaking device enters thecavity and landing the containment system on the seafloor,

g) opening the upper valve 62 for recovering the hydrocarbon fluid.

Thanks to the above method, the anti hydrates fluid AHF is in contactwith the sea water (cold) only during the last landing steps. The entirequantity of anti hydrates fluid AHF can be efficiently prevent hydratesformation.

The time delay for installing the dome 20 above the leaking device 2 canbe very short, and the risk of hydrates formation is reduced.

The containment system 1 is advantageously thermally insulated and theanti hydrates fluid AHF is advantageously heated before step b) offilling the cavity 21.

Then, the method can bring a very large quantity of relatively hot antihydrates fluid AHF just when landing the containment system 1 above theleaking device 2. Such method can be much more efficient than previouslyknown techniques.

After landing, the jet of hydrocarbon fluid from the leaking device 2 isitself heating the mix of fluids contained inside the cavity 21, andhydrates formation is therefore naturally prevented.

The embodiments above are intended to be illustrative and not limiting.Additional embodiments may be within the claims. Although the presentinvention has been described with reference to particular embodiments,workers skilled in the art will recognize that changes may be made inform and detail without departing from the spirit and scope of theinvention.

Various modifications to the invention may be apparent to one of skillin the art upon reading this disclosure. For example, persons ofordinary skill in the relevant art will recognize that the variousfeatures described for the different embodiments of the invention can besuitably combined, un-combined, and re-combined with other features,alone, or in different combinations, within the spirit of the invention.Likewise, the various features described above should all be regarded asexample embodiments, rather than limitations to the scope or spirit ofthe invention. Therefore, the above is not contemplated to limit thescope of the present invention.

1. A containment system for recovering a hydrocarbon fluid from aleaking device that is situated at the seafloor and that is leaking thehydrocarbon fluid from a well, wherein the containment system is adaptedto be landed at the seafloor corresponding to a base level of thecontainment system, and wherein the containment system comprises: a domeintended to be secured to the seafloor around the leaking device andforming a cavity under said dome, said cavity being adapted tocompletely surround and include the leaking device, and to accumulatehydrocarbon fluid coming upwardly from the leaking device, said domecomprising an upper opening to extract the hydrocarbon fluid forrecovery and a lower opening to enter the leaking device inside thecavity, an upper valve for opening or closing the upper opening, and alower closing assembly for closing the lower opening at least during amoving of the containment system from a first location near the seasurface to a second location near the seafloor, and for opening thelower opening when the containment system is being installed around theleaking device.
 2. The containment system according to claim 1, whereinthe lower opening is between 6 and 12 meters wide, and preferablybetween 8 and 10 meters wide.
 3. The containment system according toclaim 1, wherein the dome is thermally insulated with an insulatingmaterial for having an overall heat transfer coefficient of the domelower than 1 W·m⁻²·K⁻¹.
 4. The containment system according to claim 1,wherein the dome comprises a structure that is rigid for building ashape of the dome.
 5. The containment system according to claim 4,wherein the structure is composed of interconnected beams.
 6. Thecontainment system according to claim 4, wherein the dome comprises anenvelope disposed substantially inside the structure and being flexibleto adapt itself to the shape of the structure and to seal the cavity. 7.The containment system according to claim 6, wherein the envelopeextends below a lower end of the structure to form a flexible loweropening.
 8. The containment system according to claim 4, wherein thedome comprises an envelope that extends below a lower end of thestructure to form a flexible lower opening.
 9. The containment systemaccording to claim 7, wherein the lower closing assembly comprises anarrowing mechanism that is able to close up a lower end of the envelopeto close the lower opening.
 10. The containment system according toclaim 1, wherein the lower closing assembly is a door mechanismarticulated to a lower end of the dome and comprising a drivingmechanism to close or open the lower opening.
 11. The containment systemaccording to claim 1, wherein the lower closing assembly is a diaphragmmechanism positioned at a lower end of the dome and comprising a drivingmechanism to close or open the lower opening.
 12. The containment systemaccording to claim 1, wherein the lower closing assembly is a doormechanism attached to a lower end of the dome and comprising a drivingmechanism to free the door and to open the lower opening.
 13. Thecontainment system according to claim 1, wherein the lower closingassembly comprises a flexible membrane, said flexible membrane beingadapted for being penetrated by the leaking device when the containmentsystem is moved so as the leaking device enters the cavity.
 14. A methodfor using a containment system for recovering hydrocarbon fluid from aleaking device that is situated at the seafloor and that is leakinghydrocarbon fluid from a well, said containment system being adapted tobe landed at the seafloor corresponding to a base level of thecontainment system and wherein the containment system comprises: a domeintended to be secured to the seafloor around the leaking device andforming a cavity under said dome, said cavity being adapted tocompletely surround and include the leaking device, and to accumulatehydrocarbon fluid coming upwardly from the leaking device, said domecomprising an upper opening to extract the hydrocarbon fluid forrecovering and a lower opening to enter the leaking device inside thecavity, an upper valve for opening or closing the upper opening, and alower closing assembly for closing and opening the lower opening, andwherein the method comprises the following successive steps: a)providing a containment system at a first location near sea surface, b)closing the upper valve and the lower closing assembly, and filling thecavity with an anti hydrates fluid, c) moving the containment systemfrom the first location down to a second location near the leakingdevice, d) connecting a pipe to the upper opening, e) opening the loweropening by the lower closing assembly, f) moving the containment systemso as the leaking device enters the cavity, g) opening the upper valvefor recovering the hydrocarbon fluid.
 15. The method according to claim14, wherein the anti hydrates fluid is heated before the filling stepb).
 16. The method according to claim 14, wherein the anti hydratesfluid comprises one or a combination of the fluid components chosen fromthe list of water, salted water, dead oil, an alcohol, an ethanol, amethanol, a glycol, an ethylene glycol, a diethylene glycol, and alow-dosage hydrate inhibitor.